<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>盒子模型尺寸</title>
    <style>
        div{
            width: 200px;
            height: 200px;
            border: 5px solid red;
            margin-left: 50px;
            padding-left: 100px;
            box-sizing: border-box;
        }
    </style>
</head>
<body>
<div>

</div>
</body>
</html>